Asked by Hannelore
What is the probability that a 10-sided die is rolled 3 times and each time the value was unique (i.e. there are no repeating values from previous rolls)?
I know I can do this with a tree diagram fairly easily, but is there a formula for it that doesn't involve one of those? They're time-consuming.
I know I can do this with a tree diagram fairly easily, but is there a formula for it that doesn't involve one of those? They're time-consuming.
Answers
Answered by
Reiny
On the first roll, there are 10 possible outcomes.
For the second roll you want it to be different from the first, so only 9 possible outcomes, with 8 as the third
So the prob(your event) = 10*9/8/1000
= .72
For the second roll you want it to be different from the first, so only 9 possible outcomes, with 8 as the third
So the prob(your event) = 10*9/8/1000
= .72
Answered by
Hannelore
Ah awesome! Any specific reason we're dividing by 1000? Just to get the right decimal?
Answered by
MathMate
Multiplication rule:
(10/10)*(9/10)*(8/10)=10*9/8/1000
(10/10)*(9/10)*(8/10)=10*9/8/1000
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